An improved wheelchair for climbing stairs and inclined ramps has been described in U.S. patent application Ser. No. 461,654, filed Jan. 27, 1983, now U.S. Pat. No. 4,564,080. The wheelchair in this disclosure includes a number of features which permit a wheelchair or similar conveyance to change from a first wheel base comprised of ground-engaging wheels to a second wheel base comprised of a pair of endless, flexible tracks when the wheelchair is to be moved up or down an inclined path. The wheels and tracks are motor-driven, and a suitable control is provided to allow for forward and reverse movements of the wheelchair as well as turning movements of the wheelchair.
It has been found that, with a wheelchair of the type described, it is desirable to avoid rapid downward movements as the wheelchair moves from a horizontal path to an inclined path and as the wheelchair moves from an inclined path to a horizontal path. Such movements are rapid and cause an impact with a surface which causes discomfort to the user of the wheelchair, a condition to be avoided. Thus, a need has arisen for improvements in the way in which the wheelchair moves between horizontal and inclined paths to avoid such discomfort to the wheelchair user. The present invention satisfies this need.